.container {
    width: 1000px;
    margin: 0 auto;
    padding: 50px;
    text-align: center;
    position: relative;
    border: 1px solid red;
}

.clearfix:after {
    content: '';
    display: block;
    clear: both;
}


/* 立方体------- */

.cube {
    width: 200px;
    height: 200px;
    /* background: gainsboro; */
    transform-style: preserve-3d;
    /* perspective: 1500px; */
    /* transform: rotateX(30deg) rotateY(30deg); */
    position: relative;
    margin: 100px auto;
}

.face {
    width: 200px;
    height: 200px;
    position: absolute;
    opacity: 0.8;
    font-size: 2em;
    color: white;
    text-transform: uppercase;
    line-height: 200px;
    /* backface-visibility: hidden; */
    transition: all 1s linear;
}

.front {
    background-color: red;
    transform: translateZ(100px);
}

.back {
    background-color: green;
    transform: rotateY(180deg) translateZ(100px);
}

.left {
    background-color: blue;
    transform: rotateY(90deg) translateZ(100px);
}

.right {
    background-color: orange;
    transform: rotateY(-90deg) translateZ(100px);
}

.top {
    background-color: purple;
    transform: rotateX(90deg) translateZ(100px);
}

.bottom {
    background-color: black;
    transform: rotateX(-90deg) translateZ(100px);
}

.btn {
    border-radius: 50% 50%;
    width: 80px;
    height: 80px;
    background: #000000;
    color: white;
    border: none;
}